1. Field of the Invention
The present invention relates to a system for processing external data and for providing results of such processing to other devices.
2. Description of Related Art
Conventional electronic controllers, for example, a controller for controlling an internal combustion engine of a vehicle, are provided with a microprocessor. Such a microprocessor, which typically includes a CPU, ROM, RAM and the like, processes input data from the outside by executing predetermined processes based on programs stored beforehand in the ROM. Based on the results of the execution of the predetermined processes, this microprocessor provides control signals to output circuits to drive actuators or the like.
To ensure the proper execution of a control process for controlling a target device, after storing the control program in the ROM, conventional electronic controllers employ a checking procedure (i.e., check sum) to check if the original program and data are accurately stored in the ROM or not. However, the check sum procedure may not be able to check if the original program and data are stored accurately in the ROM or not when several errors occur during the storage of the control program and data in the ROM. Thus, the electronic controller might perform control operations based on such erroneous program and data. Moreover, such program errors may appear inconspicuous during normal control operations and thus, it will be difficult to detect such errors.
Meanwhile, the electronic controller may be further provided with a monitor circuit to check if the CPU generates watchdog signals at regular intervals or not. However, in this arrangement, the monitor circuit will only be simply monitoring the generation of watchdog signals performed by the CPU based on a separate output procedure. Thus, the monitor circuit might not be able to detect actual errors in the control program being performed by the CPU.